gold farm not exactly working

[fullofchagrin]

im afking on the platform by the nether portal, i don't really need gold rn but i took some from the chests earlier so i want to make it up. i afked for about half an hour but the chests were empty, i did see some pigmen falling down earlier when i jumped down, so i don't get if i'm doing something wrong?

 

[fullofchagrin]

i just afked again for a few minutes, a couple of pigmen fall down when i jump down, but for the rest it's not working it's only generating a few gold nuggets

 

[fullofchagrin]

i afked for 1.5 hour, this time it worked, although there is less than a double chest amount of nuggets, is that a typical drop rate?